Herpesviridae

The Herpesviridae are a large family of DNA viruses that cause diseases in humans and animals.^{[1] [2] [3]} The family name is derived from the Greek word herpein ("to creep"), referring to the latent, re-occurring infections typical of this group of viruses. Herpesviridae can cause latent or lytic infections.

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Human herpesviridae

There are eight distinct viruses in this family known to cause disease in humans.^[4]

Monkey B virus (Cercopithecine herpesvirus-1, Herpesvirus simiae) is a simplexvirus endemic in macaque monkeys. Human zoonotic infection typically results in fatal encephalomyelitis or severe neurologic impairment in untreated individuals.^[6]

Viral structure

The human herpesviruses all share some common properties. One shared property is virus structure—all herpesviruses are composed of relatively large double-stranded, linear DNA genomes encoding 100-200 genes encased within an icosahedral protein cage called the capsid which is itself wrapped in a lipid bilayer membrane called the envelope. This particle is known as the virion.

Following binding of viral envelope glycoproteins to cell membrane receptors, the virion is internalized and dismantled, allowing viral DNA to migrate to the cell nucleus. Within the nucleus, replication of viral DNA and transcription of viral genes occurs. During symptomatic infection, infected cells transcribe lytic viral genes. In some host cells, a small number of viral genes termed latency associated transcript (LAT) accumulate instead. In this fashion the virus can persist in the cell (and thus the host) indefinitely. Reactivation of latent viruses has been implicated in a number of organic diseases. While primary infection is often accompanied by a self-limited period of clinical illness, long-term latency is symptom-free. Following activation, transcription of viral genes switches from LAT to multiple lytic genes that lead to enhanced replication and virus production. Often, lytic activation leads to cell death. Clinically, lytic activation is often accompanied by emergence of non-specific symptoms such as low grade fever, headache, sore throat, malaise, and rash as well as clinical signs such as swollen or tender lymph nodes and immunological findings such as reduced levels of natural killer cells.

Animal herpesviridae

In animal virology the most important herpesviruses belong to the Alphaherpesvirinae. Research on pseudorabies virus (PrV), the causative agent of Aujeszky's disease in pigs, has pioneered animal disease control with genetically modified vaccines. PrV is now extensively studied as a model for basic processes during lytic herpesvirus infection, and for unravelling molecular mechanisms of herpesvirus neurotropism, whereas bovine herpesvirus 1, the causative agent of bovine infectious rhinotracheitis and pustular vulvovaginitis, is analyzed to elucidate molecular mechanisms of latency. The avian infectious laryngotracheitis virus is phylogenetically distant from these two viruses and serves to underline similarity and diversity within the Alphaherpesvirinae.^{[2] [3]}

• Subfamily Alphaherpesvirinae
  • Genus Simplexvirus
    • Bovine herpesvirus 2 causes bovine mammillitis and pseudo-lumpyskin disease.
    • Cercopithecine herpesvirus 1, also known as Herpes B virus, causes a Herpes simplex-like disease in Macaques.
    • Ateline herpesvirus 1, Spider monkey herpesvirus.
  • Genus Varicellovirus
    • Bovine herpesvirus 1 causes infectious bovine rhinotracheitis, vaginitis, balanoposthitis, and abortion in cattle.
    • Bovine herpesvirus 5 causes encephalitis in cattle.
    • Caprine herpesvirus 1 causes conjunctivitis and respiratory disease in goats.
    • Porcine herpesvirus 1 causes pseudorabies.
    • Equine herpesvirus 1 causes abortion in horses.
    • Equine herpesvirus 3 causes coital exanthema in horses.
    • Equine herpesvirus 4 causes rhinopneumonitis in horses.
    • Canine herpesvirus 1 causes a severe hemorrhagic disease in puppies.
    • Feline herpesvirus 1 causes feline viral rhinotracheitis and keratitis in cats.
    • Duck herpesvirus 1 causes duck plague.
  • Genus Mardivirus
    • Gallid herpesvirus 2 causes Marek's disease.
    • Gallid herpesvirus 3 (GaHV-3 or MDV-2)
    • Herpesvirus of turkeys (HVT)
  • Genus Iltovirus
    • Gallid herpesvirus 1 causes infectious laryngotracheitis in birds.
• Subfamily Betaherpesvirinae
  • Porcine herpesvirus 2 causes inclusion body rhinitis in swine.
• Subfamily Gammaherpesvirinae
  • Genus Rhadinovirus
    • Alcelaphine herpesvirus 1 causes bovine malignant catarrhal fever.
    • Bovine herpesvirus 4
    • Equine herpesvirus 2 causes equine cytomegalovirus infection.
    • Equine herpesvirus 5 ^[7]

Taxonomy

The following genera are included here:

• Subfamily Alphaherpesvirinae
  • Genus Simplexvirus; type species: Human herpesvirus 1 or Herpes simplex; diseases: cold sores, genital herpes, encephalitis
  • Genus Varicellovirus; type species: Human herpesvirus 3 or Varicella-zoster virus; diseases: chickenpox, shingles
  • Genus Mardivirus; type species: Gallid herpesvirus 2
  • Genus Iltovirus; type species: Gallid herpesvirus 1
• Subfamily Betaherpesvirinae
  • Genus Cytomegalovirus; type species: Human herpesvirus 5; diseases: mononucleosis
  • Genus Muromegalovirus; type species: Murid herpesvirus 1
  • Genus Roseolovirus; type species: Human herpesvirus 6; diseases: erythema subitum, roseola infantum
• Subfamily Gammaherpesvirinae
  • Genus Lymphocryptovirus; type species: Human herpesvirus 4 or Epstein-Barr virus; diseases: mononucleosis, Burkitt's lymphoma, nasopharyngeal carcinoma, Hodgkin's disease
  • Genus Rhadinovirus; type species: Human Herpesvirus 8, Saimiriine herpesvirus 2
• Unassigned
  • Genus Cercopithecine; type species: Cercopithecine herpesvirus 1
  • Genus Ictalurivirus; type species: Ictalurid herpesvirus 1

References